1. Field of Invention
The invention relates to an exhaust emission control system in a vehicle including a plurality of engines.
2. Description of Related Art
JP-A-6-93855 (pp.3–4, FIG. 1) discloses a vehicle including two engines, that is, a primary engine and a secondary engine, one or both of which may be operated for driving in accordance with the running state. In the aforementioned vehicle of the publication, exhaust gas discharged from the primary engine is supplied to a turbine of a turbocharger via an exhaust manifold that extends to the rear of the primary engine, and is further supplied to a case that contains an exhaust catalyst via an exhaust pipe. The exhaust gas then flows into a silencer via an exhaust pipe provided downstream of the catalyst for noise muffling, and is finally discharged into atmosphere. The exhaust gas discharged from the secondary engine is supplied to an exhaust pipe provided downstream of the exhaust catalyst via an exhaust manifold that extends to the rear of the secondary engine so as to join the exhaust gas discharged from the primary engine.
In the aforementioned type of the vehicle, however, the exhaust gas from the secondary engine joins the exhaust gas from the primary engine at a point downstream of the exhaust catalyst, and then discharged into atmosphere. That is, the exhaust gas from the secondary engine is discharged into atmosphere without having its harmful components removed.